feat: Initialize SvelteKit project, add tsconfig.json, and introduce a new Calculator.svelte component.

hdyc-svelte/src/routes/+layout.svelte

@@ -0,0 +1,37 @@
+<script lang="ts">
+  import '../app.css';
+  import Sidebar from '$lib/components/Sidebar.svelte';
+  import SearchBar from '$lib/components/SearchBar.svelte';
+
+  let sidebarOpen = false;
+</script>
+
+<svelte:head>
+  <meta name="viewport" content="width=device-width, initial-scale=1" />
+  <link rel="icon" href="/favicon.png" />
+</svelte:head>
+
+<header class="site-header">
+  <div style="display:flex;align-items:center;gap:0.75rem;">
+    <button class="hamburger" on:click={() => (sidebarOpen = !sidebarOpen)} aria-label="Toggle menu">
+      ☰
+    </button>
+    <a href="/" class="site-logo">
+      <span>How Do You</span><span class="logo-accent">Convert</span><span style="opacity:0.4;font-weight:400">.com</span>
+    </a>
+  </div>
+  <div class="header-right">
+    <SearchBar />
+  </div>
+</header>
+
+<div class="site-body">
+  <Sidebar bind:open={sidebarOpen} />
+  <main class="main-content">
+    <slot />
+  </main>
+</div>
+
+<footer class="site-footer">
+  © {new Date().getFullYear()} HowDoYouConvert.com — Free unit conversion calculators. All rights reserved.
+</footer>